1. Field of Invention
The present invention relates generally to tunnel type laser scanning systems arranged about a high-speed conveyor system used in diverse package routing and transport applications, and also a method of scanning bar code symbols on surfaces facing any direction with a 3-D scanning volume disposed above the conveyor system.
2. Brief Description of the Prior Art
In many environments, there is a great need to automatically identify objects (e.g. packages, parcels, products, luggage, etc.) as they are transported along a conveyor structure. While over-the-head laser scanning systems are effective in scanning upwardly-facing bar codes on conveyed objects, there are many applications where it is not practical or otherwise feasible to ensure that bar code labels are upwardly-facing during transported under the scanning station.
Various types of xe2x80x9ctunnelxe2x80x9d scanning systems have been proposed so that bar codes can be scanned independent of their orientation within scanning volume of the system. One such prior art tunnel scanning system is disclosed in U.S. Pat. No. 5,019,714 to Knowles. In this prior art scanning system, a plurality of single scanline scanners are orientated about a conveyor structure in order to provide limited degree of omni-directional scanning within the xe2x80x9ctunnel-likexe2x80x9d scanning environment. Notably, however, prior art tunnel scanning systems, including the system disclosed in U.S. Pat. No. 5,019,714, are incapable of scanning bar code systems in a true omni-directional sense, i.e. independent of the direction that the bar code faces as it is transported along the conveyor structure. At best, prior art scanning systems provide omni-directional scanning in the plane of the conveyor belt or in portions of planes orthogonal thereto. However, true omnidirectional scanning along the principal planes of a large 3-D scanning volume has not been hitherto possible.
Thus, there is a great need in the art for an improved tunnel-type laser scanning system and a method of scanning bar code symbols on packages being transported along a high-speed conveyor system, while avoiding the shortcomings and drawbacks of prior art scanning systems and methodologies.
Accordingly, a primary object of the present invention is to provide a novel omni-directional tunnel-type laser scanning system that is free of the shortcomings and drawbacks of prior art tunnel-type laser scanning systems and methodologies.
Another object of the present invention is to provide such a tunnel-type laser scanning system, wherein bar code symbols that have been placed on any surface of any package, including USPS trays and tubs, and other customer mailed products, including the bottom surface of the product, are automatically scanned during movement through the system.
Another object of the present invention is to provide such a tunnel-type scanning system which can be used for high speed mail and parcel sorting systems (e.g. Large Package Sorting Systems (LPSS), Singulate and Scan Induction Units (SSIU), as well as luggage checking and tracking systems used in airport terminals, bus-stations, train stations, and the like.
Another object of the present invention is to provide such tunnel-type scanning system, which can read different bar code symbologies (e.g. Interleaved two of five, Code 128 and Code three of nine), code lengths, and formats in accordance with AIM and ANSI Standards.
Another object of the present invention is to provide such a tunnel-type scanning system, in which a user-interface is provided for programming the bar code symbologies, code lengths and code formats handled by each laser scanning unit within the system.
Another object of the present invention is to provide such a tunnel-type scanning system, for reading bar code symbols on packages having various types of symbol formats, such as ZIP Code symbols (six digits), Package Identification Code (PIC) symbols (sixteen characters), and Tray bar code symbols (ten digits).
Another object of the present invention is to provide such a tunnel-type scanning system, for omni-directional scanning of bar code symbols on packages, parcels and products transported along a high-speed conveyor system at velocities in the range of about 100 to 520 feet per minute or greater.
Another object of the present invention is to provide such a tunnel-type scanning system, in which a plurality of holographic laser scanning subsystems are mounted from a scanner support framework arranged about a high-speed conveyor belt, and arranged so that each scanning subsystem projects a highly-defined 3-D omni-directional scanning volume with a large depth-of-field, above the conveyor structure so as to collectively provide omni-directional scanning within each of the three principal scanning planes of the tunnel-type scanning system.
Another object of the present invention is to provide such a tunnel-type scanning system, in which each holographic laser scanning subsystem projects a highly-defined 3-D omni-directional scanning volume that has a large depth-of-field and is substantially free of spatially and temporally coincident scanning planes, to ensure substantially zero crosstalk among the numerous laser scanning channels provided within each holographic laser scanning subsystem employed in the system.
Another object of the present invention is to provide such a tunnel-type scanning system, in which a split-type conveyor is used with a gap disposed between its first and second conveyor platforms, for mounting of an omni-directional projection-type laser scanning subsystem that is below the conveyor platforms and extends substantially the entire width of the conveyor platform.
Another object of the present invention is to provide such a tunnel-type scanning system, wherein a plurality of holographic laser scanners are arranged about the conveyor system to produce a bi-directional scanning pattern along the principal axes of a three-dimensional laser scanning volume.
A further object of the present invention is to provide such a tunnel-type scanning system, in which each holographic laser scanner employed in the system projects a three-dimensional laser scanning volume having multiple focal planes and a highly confined geometry extending about a projection axis extending from the scanning window of the holographic scanner and above the conveyor belt of the system.
Another object of the present invention is to provide an improved tunnel-type scanning system, wherein bar code symbols downwardly facing the conveyor belt can be automatically scanned as they are transported through the system in a high-speed manner.
Another object of the present invention is to provide an improved method of scanning bar code symbols within a tunnel-scanning environment through which objects of various types can be conveyed at high transport speeds.
These and other objects of the present invention will become apparent hereinafter and in the Claims to Invention.